Combined Air Release Valves For Pipelines

Jul 27, 2023 | News

Trapped air pockets and accumulated gases within liquid pipeline systems can cause numerous operational problems. Air reduces the effective cross-section for liquid flow, increasing head loss. Air pockets create hydraulic disturbances that lead to pressure surges and water hammer effects. Under pressure, dissolved gases come out of solution forming bubbles that lower pump efficiency and damage components. Removing detrimental accumulated air and maintaining the system full of liquid is critical for efficient hydraulic transport. This is achieved by installing air release valves at strategic locations in the pipeline.

Combined air release valve, also known as Triple funcations air vents, perform the vital functions of air release, air intake, and surge alleviation within a single compact device. These versatile valves automatically remove accumulated air and gases during system filling and operation. They also break vacuum conditions during pipeline drainage and draw in air to prevent column separation. Under emergency conditions, they instantly release surges of air and fluid to minimize the damaging effects of water hammer.

air release valve

Working Principle Of Air Release Valves

Combined air release valve works on the principle of differential pressure between the pressurized pipeline system and atmosphere. As liquid fills the empty pipeline, air pockets get compressed and travel to high points along the line.

The valve inlet is connected to the top of the pipe at these high points. When the liquid level reaches the valve inlet, compressed air is released. Floats within the valve rise with the liquid level, unseating the main orifice. Compressed air pushes past the floats and discharges to atmosphere. Cleaning specific air release orifices also open to vent small pockets of air.

After the system is filled and pressurized, gases released from solution accumulate at the valve inlet. The floats drop and the main orifice closes. The small air release orifices continue venting, steadily removing the accumulated gases.

If the upstream liquid pressure drops due to draining or column separation, the floats also drop. This opens the large air intake orifice, allowing air to enter and prevent vacuum conditions.

In case of sudden surges, increased pressure instantly compresses the air pocket under the floats. The main orifice rapidly releases the air like a shock absorber, limiting the pressure rise.

Key Features Of Combined Air Release Valve

  • Releases accumulated air during filling. Permits rapid system filling.
  • Vents released gases during pressurized operation. Maintains peak hydraulic efficiency.
  • Prevents destructive vacuum conditions and column separation.
  • Alleviates pressure surges during transients. Minimizes water hammer damage.
  • Handles large air volumes at high flow rates. Copes with air slugs and column separation.
  • Withstands high inlet pressures up to 150 psi. Rated for liquid temperatures up to 200°F.
  • Floats and orifices designed to resist fouling, corrosion and abrasion.
  • Compact and light weight. Easy to install in cramped spaces.
  • Minimum maintenance. No power or controls required.

Combined air release valves are vital protective devices for liquid pipeline systems. By performing the crucial functions of air venting, air intake and surge alleviation, they enhance hydraulic efficiency, prevent vacuum damage, and reduce water hammer effects. Their automatic operation and compact envelope makes them an indispensable component for reliable and safe pipeline operation. They continue working 24/7 to keep the system primed and ready for service.

Quick Release Air Valves

While combined air release valves handle normal air and gas venting, more specialized quick release valves are required for rapid discharge of large air volumes. These valves rapidly vent air slugs at extremely high flow rates, preventing destructive pressure transients during events like pump start-up and power outages.

Quick release air valve has a lightweight ball that floats on the liquid surface within the valve body. During normal operation, the ball floats at its lowest position, fully sealing the valve outlet. In case of emergency air discharge, inlet pressure thrusts the ball upwards within a cage. The ball lifts only slightly before coming to rest on cage stops. This movement uncovers the seat and creates a narrow gap around the ball.

The small annular gap exposes a very large outlet orifice area given the large diameter of the valve. As air slugs rush into the valve inlet, they push past the ball, accelerate through the gap, and discharge at very high velocities. Flow rates of 15,000 GPM or more are common. The intense venting rapidly relieves the air pressure, minimizing damaging water hammer effects.

By incorporating both combined air release and quick release valves, pipeline systems can be protected from internal air and pressure transients throughout their operating cycle. The combined action keeps the pipeline primed for efficient hydraulic performance while preventing catastrophic damage.